Haldeman's protagonist, William Mandella, is, in the late nineties of the last century (consider this book was written in the 1970s), drafted into a UNOelite force tasked with guarding so-called portal planets, that is, lightless worlds circling collapsars, stars frozen in a state of perpetual collapse that make faster-than-light travel a reality. An ever-increasing number of spaceships has been lost to unknown aliens called "Taurans" for lack of a better name, and Mandella's job is supposed to be kicking their rear in close combat.

The military has made all "moral issues" of Vietnam doctrine by now. Ceaseless pot-smoking and forced libertinage among male and female soldiers are a part of Mandella's everyday life. In basic training already, live ammo is used, and the training outfit sufferss enormous losses. After his training, Mandella plays part in several raids on portal planets. He experiences the first-ever ground assault against Taurans; a shuttle crash that costs him a leg; an assault that has to be aborted before landing; and in the end, an officer by then, he commands a company defending a base on one of the portal planets.

He lives through the entire war, which means just a couple of years for him, though in the meantime, he returns once to an Earth that has become utterly strange, and once to a luxury rest-and-recreation planet that depends completely on the military. Because of time dilatation when making "collapsar jumps", more than a millennium passes for an Earthside observer.

Haldeman describes futuristic war technology that is beyond human scale in every respect, and which even the soldiers have trouble mastering. No mention of higher goals, of glory and honour is ever made. The author does not embellish anything, and he's definitely not squeamish: he kills even characters with names and faces suddenly and without any heroism.

The small amount of handwaving in this book (mainly restricted to a "tachyon" energy source and the "collapsar jump") is easily accepted for the sake of the plot. Other than that, the universe of the Forever War is presented in a frighteningly realistic and scientifically plausible way. The enemy is nearly impossible to seize; weapons react faster than humans can think; walnut-sized missiles tear gigantic space vessels almost to pieces due to their immense kinetic energy. At the end, Mandella can only prevent the loss of his entire company because he realises in time what it means to planet if a spaceship of several million tonnes impacts it at relativistic speed.

Probably the most moving scene of the book is the one where Mandella's lover and comrade Marygay is wounded terribly, not in any combat, but by lifeless machinery, to be exact: a crease in her acceleration suit, and the medics fight for her life. This chapter incorporates the very concept of the book in its purest form: The Taurans are not really the enemy, not any more than the Entente soldiers in "All Quiet on the Western Front" are the enemy.

This book is not only remarkable for being science fiction well done, but it's got a worth of its own. It's not just run-of-the-mill plotwork with a science fiction icing, but the plot lives through its hypothetical background. "The Forever War" is a must for every science fiction reader and highly recommended to anyone else who enjoys an intelligent novel.